Brandy should not be suspended. Hell is a place and she used it in that context when she said 'You're going to go to hell for swearing to God'.
If Brady told the boy something like "You go to h*ll" or "h*ll no!" or used it in a profane manner, then she was wrong in this situation.
In either situation though, whether she said it as a curse word or as the name of a place, suspension is too much. The teacher could have just pulled her aside and explain to her why she shouldn't use such language (or if she must be punished, make her miss recess for a week).
Ahhh, what happened to the days of good 'ol corporal punishment.
